Geothermal energy



Geothermal is defined as the discipline of Earth Sciences that studies the set of natural phenomena involved in the production and transfer of heat or thermal energy from inside the Earth.

What is the difference between geothermal and geothermal energy?

In a broad sense, the geothermal concept can also be extended to the study of other planets. Its principles are exploited at the technological level in the production of electricity and in cogeneration through geothermal power plants from the associated geothermal energy.

In conclusion, geothermal is the relationship between the Earth and the heat generated by it. On the other hand, there is the geothermal energy that is a related but distinct concept. Geothermal energy is the use of these natural conditions to take advantage of this thermal energy. The energy used can be in the form of heat or in the form of electricity. In any case, it is a renewable energy source since the thermal resources inside the Earth are practically inexhaustible.

The origin of the terrestrial heat of geothermal energy

The heat of the Earth's core was originally generated during the accretion of the planet developed thanks to the force of gravitational attraction. Subsequently, heat continued to be generated thanks to the natural processes of nuclear fission of elements such as uranium, thorium and potassium.

The terrestrial heat is transferred from the interior to the Earth's surface through the Earth's mantle by convection produced by the movement of magma or deep water: This is the origin of most phenomena such as volcanic eruptions, and other associated geothermal phenomena and thus evident on the surface of the earth, such as thermal springs, geysers and fumaroles.

This natural heat can be exploited for energy, specifically called geothermal energy. The term geothermal is often used to indicate precisely the exploitation of geothermal energy.

The heat flux from inside the Earth is only 1 / 20,000 of the heat that Earth receives from the sun.

What is the thermal gradient?

Depending on the heat flux and thermal conductivity, which varies according to the type of soil or rock, a different thermal gradient is observed (temperature variation as a function of depth).

 This gradient can vary from 1 ° C every 30 m of the surface part of the earth's crust to 1 ° C every 10 - 15 m of the seabed around the oceanic mountain ranges. The geothermal gradient in turn is strongly influenced by the circulation of internal terrestrial fluids.

Temperature measurement and thermal gradient

The measurement is carried out with the appropriate instruments that are dropped into the geothermal wells. Accurate temperature measurement is complex and is disturbed by heat due to perforation and the presence of liquids (water, humidity, air) may be present in the soil.

The precise measurement of the temperature is the precision that is a function of the machinery used and the purpose of the type of instrument investigation.

Instruments for measuring temperature in geothermal wells

Thermometers used in geothermal investigations must have two important characteristics:

  • Speed, therefore, must quickly reach thermal equilibrium. To have speed, therefore, these thermometers must have low thermal inertia.
  • Reading should be possible when standing outside the well.

The thermometers used can therefore be distinguished in:

  • Thermocouples (3/100 degree error)
  • Resistance thermometers (1/100 degree error)
  • Oscillators (error less than 1/1000 degrees)
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Last review: May 30, 2019